/** * The functions provided by this module are used to communicate certain properties * about the currently running code so that Next.js can make decisions on how to handle * the current execution in different rendering modes such as pre-rendering, resuming, and SSR. * * Today Next.js treats all code as potentially static. Certain APIs may only make sense when dynamically rendering. * Traditionally this meant deopting the entire render to dynamic however with PPR we can now deopt parts * of a React tree as dynamic while still keeping other parts static. There are really two different kinds of * Dynamic indications. * * The first is simply an intention to be dynamic. unstable_noStore is an example of this where * the currently executing code simply declares that the current scope is dynamic but if you use it * inside unstable_cache it can still be cached. This type of indication can be removed if we ever * make the default dynamic to begin with because the only way you would ever be static is inside * a cache scope which this indication does not affect. * * The second is an indication that a dynamic data source was read. This is a stronger form of dynamic * because it means that it is inappropriate to cache this at all. using a dynamic data source inside * unstable_cache should error. If you want to use some dynamic data inside unstable_cache you should * read that data outside the cache and pass it in as an argument to the cached function. */ import type { WorkStore } from '../app-render/work-async-storage.external' import type { WorkUnitStore, RequestStore, PrerenderStoreLegacy, PrerenderStoreModern, } from '../app-render/work-unit-async-storage.external' // Once postpone is in stable we should switch to importing the postpone export directly import React from 'react' import { DynamicServerError } from '../../client/components/hooks-server-context' import { StaticGenBailoutError } from '../../client/components/static-generation-bailout' import { workUnitAsyncStorage } from './work-unit-async-storage.external' import { workAsyncStorage } from '../app-render/work-async-storage.external' import { makeHangingPromise } from '../dynamic-rendering-utils' import { METADATA_BOUNDARY_NAME, VIEWPORT_BOUNDARY_NAME, OUTLET_BOUNDARY_NAME, } from '../../lib/metadata/metadata-constants' import { scheduleOnNextTick } from '../../lib/scheduler' import { BailoutToCSRError } from '../../shared/lib/lazy-dynamic/bailout-to-csr' import { InvariantError } from '../../shared/lib/invariant-error' const hasPostpone = typeof React.unstable_postpone === 'function' export type DynamicAccess = { /** * If debugging, this will contain the stack trace of where the dynamic access * occurred. This is used to provide more information to the user about why * their page is being rendered dynamically. */ stack?: string /** * The expression that was accessed dynamically. */ expression: string } // Stores dynamic reasons used during an RSC render. export type DynamicTrackingState = { /** * When true, stack information will also be tracked during dynamic access. */ readonly isDebugDynamicAccesses: boolean | undefined /** * The dynamic accesses that occurred during the render. */ readonly dynamicAccesses: Array syncDynamicErrorWithStack: null | Error } // Stores dynamic reasons used during an SSR render. export type DynamicValidationState = { hasSuspenseAboveBody: boolean hasDynamicMetadata: boolean hasDynamicViewport: boolean hasAllowedDynamic: boolean dynamicErrors: Array } export function createDynamicTrackingState( isDebugDynamicAccesses: boolean | undefined ): DynamicTrackingState { return { isDebugDynamicAccesses, dynamicAccesses: [], syncDynamicErrorWithStack: null, } } export function createDynamicValidationState(): DynamicValidationState { return { hasSuspenseAboveBody: false, hasDynamicMetadata: false, hasDynamicViewport: false, hasAllowedDynamic: false, dynamicErrors: [], } } export function getFirstDynamicReason( trackingState: DynamicTrackingState ): undefined | string { return trackingState.dynamicAccesses[0]?.expression } /** * This function communicates that the current scope should be treated as dynamic. * * In most cases this function is a no-op but if called during * a PPR prerender it will postpone the current sub-tree and calling * it during a normal prerender will cause the entire prerender to abort */ export function markCurrentScopeAsDynamic( store: WorkStore, workUnitStore: undefined | Exclude, expression: string ): void { if (workUnitStore) { switch (workUnitStore.type) { case 'cache': case 'unstable-cache': // Inside cache scopes, marking a scope as dynamic has no effect, // because the outer cache scope creates a cache boundary. This is // subtly different from reading a dynamic data source, which is // forbidden inside a cache scope. return case 'private-cache': // A private cache scope is already dynamic by definition. return case 'prerender-legacy': case 'prerender-ppr': case 'request': break default: workUnitStore satisfies never } } // If we're forcing dynamic rendering or we're forcing static rendering, we // don't need to do anything here because the entire page is already dynamic // or it's static and it should not throw or postpone here. if (store.forceDynamic || store.forceStatic) return if (store.dynamicShouldError) { throw new StaticGenBailoutError( `Route ${store.route} with \`dynamic = "error"\` couldn't be rendered statically because it used \`${expression}\`. See more info here: https://nextjs.org/docs/app/building-your-application/rendering/static-and-dynamic#dynamic-rendering` ) } if (workUnitStore) { switch (workUnitStore.type) { case 'prerender-ppr': return postponeWithTracking( store.route, expression, workUnitStore.dynamicTracking ) case 'prerender-legacy': workUnitStore.revalidate = 0 // We aren't prerendering, but we are generating a static page. We need // to bail out of static generation. const err = new DynamicServerError( `Route ${store.route} couldn't be rendered statically because it used ${expression}. See more info here: https://nextjs.org/docs/messages/dynamic-server-error` ) store.dynamicUsageDescription = expression store.dynamicUsageStack = err.stack throw err case 'request': if (process.env.NODE_ENV !== 'production') { workUnitStore.usedDynamic = true } break default: workUnitStore satisfies never } } } /** * This function is meant to be used when prerendering without cacheComponents or PPR. * When called during a build it will cause Next.js to consider the route as dynamic. * * @internal */ export function throwToInterruptStaticGeneration( expression: string, store: WorkStore, prerenderStore: PrerenderStoreLegacy ): never { // We aren't prerendering but we are generating a static page. We need to bail out of static generation const err = new DynamicServerError( `Route ${store.route} couldn't be rendered statically because it used \`${expression}\`. See more info here: https://nextjs.org/docs/messages/dynamic-server-error` ) prerenderStore.revalidate = 0 store.dynamicUsageDescription = expression store.dynamicUsageStack = err.stack throw err } /** * This function should be used to track whether something dynamic happened even when * we are in a dynamic render. This is useful for Dev where all renders are dynamic but * we still track whether dynamic APIs were accessed for helpful messaging * * @internal */ export function trackDynamicDataInDynamicRender(workUnitStore: WorkUnitStore) { switch (workUnitStore.type) { case 'cache': case 'unstable-cache': // Inside cache scopes, marking a scope as dynamic has no effect, // because the outer cache scope creates a cache boundary. This is // subtly different from reading a dynamic data source, which is // forbidden inside a cache scope. return case 'private-cache': // A private cache scope is already dynamic by definition. return case 'prerender': case 'prerender-legacy': case 'prerender-ppr': case 'prerender-client': break case 'request': if (process.env.NODE_ENV !== 'production') { workUnitStore.usedDynamic = true } break default: workUnitStore satisfies never } } function abortOnSynchronousDynamicDataAccess( route: string, expression: string, prerenderStore: PrerenderStoreModern ): void { const reason = `Route ${route} needs to bail out of prerendering at this point because it used ${expression}.` const error = createPrerenderInterruptedError(reason) prerenderStore.controller.abort(error) const dynamicTracking = prerenderStore.dynamicTracking if (dynamicTracking) { dynamicTracking.dynamicAccesses.push({ // When we aren't debugging, we don't need to create another error for the // stack trace. stack: dynamicTracking.isDebugDynamicAccesses ? new Error().stack : undefined, expression, }) } } export function abortOnSynchronousPlatformIOAccess( route: string, expression: string, errorWithStack: Error, prerenderStore: PrerenderStoreModern ): void { const dynamicTracking = prerenderStore.dynamicTracking abortOnSynchronousDynamicDataAccess(route, expression, prerenderStore) // It is important that we set this tracking value after aborting. Aborts are executed // synchronously except for the case where you abort during render itself. By setting this // value late we can use it to determine if any of the aborted tasks are the task that // called the sync IO expression in the first place. if (dynamicTracking) { if (dynamicTracking.syncDynamicErrorWithStack === null) { dynamicTracking.syncDynamicErrorWithStack = errorWithStack } } } export function trackSynchronousPlatformIOAccessInDev( requestStore: RequestStore ): void { // We don't actually have a controller to abort but we do the semantic equivalent by // advancing the request store out of prerender mode requestStore.prerenderPhase = false } /** * use this function when prerendering with cacheComponents. If we are doing a * prospective prerender we don't actually abort because we want to discover * all caches for the shell. If this is the actual prerender we do abort. * * This function accepts a prerenderStore but the caller should ensure we're * actually running in cacheComponents mode. * * @internal */ export function abortAndThrowOnSynchronousRequestDataAccess( route: string, expression: string, errorWithStack: Error, prerenderStore: PrerenderStoreModern ): never { const prerenderSignal = prerenderStore.controller.signal if (prerenderSignal.aborted === false) { // TODO it would be better to move this aborted check into the callsite so we can avoid making // the error object when it isn't relevant to the aborting of the prerender however // since we need the throw semantics regardless of whether we abort it is easier to land // this way. See how this was handled with `abortOnSynchronousPlatformIOAccess` for a closer // to ideal implementation abortOnSynchronousDynamicDataAccess(route, expression, prerenderStore) // It is important that we set this tracking value after aborting. Aborts are executed // synchronously except for the case where you abort during render itself. By setting this // value late we can use it to determine if any of the aborted tasks are the task that // called the sync IO expression in the first place. const dynamicTracking = prerenderStore.dynamicTracking if (dynamicTracking) { if (dynamicTracking.syncDynamicErrorWithStack === null) { dynamicTracking.syncDynamicErrorWithStack = errorWithStack } } } throw createPrerenderInterruptedError( `Route ${route} needs to bail out of prerendering at this point because it used ${expression}.` ) } // For now these implementations are the same so we just reexport export const trackSynchronousRequestDataAccessInDev = trackSynchronousPlatformIOAccessInDev /** * This component will call `React.postpone` that throws the postponed error. */ type PostponeProps = { reason: string route: string } export function Postpone({ reason, route }: PostponeProps): never { const prerenderStore = workUnitAsyncStorage.getStore() const dynamicTracking = prerenderStore && prerenderStore.type === 'prerender-ppr' ? prerenderStore.dynamicTracking : null postponeWithTracking(route, reason, dynamicTracking) } export function postponeWithTracking( route: string, expression: string, dynamicTracking: null | DynamicTrackingState ): never { assertPostpone() if (dynamicTracking) { dynamicTracking.dynamicAccesses.push({ // When we aren't debugging, we don't need to create another error for the // stack trace. stack: dynamicTracking.isDebugDynamicAccesses ? new Error().stack : undefined, expression, }) } React.unstable_postpone(createPostponeReason(route, expression)) } function createPostponeReason(route: string, expression: string) { return ( `Route ${route} needs to bail out of prerendering at this point because it used ${expression}. ` + `React throws this special object to indicate where. It should not be caught by ` + `your own try/catch. Learn more: https://nextjs.org/docs/messages/ppr-caught-error` ) } export function isDynamicPostpone(err: unknown) { if ( typeof err === 'object' && err !== null && typeof (err as any).message === 'string' ) { return isDynamicPostponeReason((err as any).message) } return false } function isDynamicPostponeReason(reason: string) { return ( reason.includes( 'needs to bail out of prerendering at this point because it used' ) && reason.includes( 'Learn more: https://nextjs.org/docs/messages/ppr-caught-error' ) ) } if (isDynamicPostponeReason(createPostponeReason('%%%', '^^^')) === false) { throw new Error( 'Invariant: isDynamicPostpone misidentified a postpone reason. This is a bug in Next.js' ) } const NEXT_PRERENDER_INTERRUPTED = 'NEXT_PRERENDER_INTERRUPTED' function createPrerenderInterruptedError(message: string): Error { const error = new Error(message) ;(error as any).digest = NEXT_PRERENDER_INTERRUPTED return error } type DigestError = Error & { digest: string } export function isPrerenderInterruptedError( error: unknown ): error is DigestError { return ( typeof error === 'object' && error !== null && (error as any).digest === NEXT_PRERENDER_INTERRUPTED && 'name' in error && 'message' in error && error instanceof Error ) } export function accessedDynamicData( dynamicAccesses: Array ): boolean { return dynamicAccesses.length > 0 } export function consumeDynamicAccess( serverDynamic: DynamicTrackingState, clientDynamic: DynamicTrackingState ): DynamicTrackingState['dynamicAccesses'] { // We mutate because we only call this once we are no longer writing // to the dynamicTrackingState and it's more efficient than creating a new // array. serverDynamic.dynamicAccesses.push(...clientDynamic.dynamicAccesses) return serverDynamic.dynamicAccesses } export function formatDynamicAPIAccesses( dynamicAccesses: Array ): string[] { return dynamicAccesses .filter( (access): access is Required => typeof access.stack === 'string' && access.stack.length > 0 ) .map(({ expression, stack }) => { stack = stack .split('\n') // Remove the "Error: " prefix from the first line of the stack trace as // well as the first 4 lines of the stack trace which is the distance // from the user code and the `new Error().stack` call. .slice(4) .filter((line) => { // Exclude Next.js internals from the stack trace. if (line.includes('node_modules/next/')) { return false } // Exclude anonymous functions from the stack trace. if (line.includes(' ()')) { return false } // Exclude Node.js internals from the stack trace. if (line.includes(' (node:')) { return false } return true }) .join('\n') return `Dynamic API Usage Debug - ${expression}:\n${stack}` }) } function assertPostpone() { if (!hasPostpone) { throw new Error( `Invariant: React.unstable_postpone is not defined. This suggests the wrong version of React was loaded. This is a bug in Next.js` ) } } /** * This is a bit of a hack to allow us to abort a render using a Postpone instance instead of an Error which changes React's * abort semantics slightly. */ export function createRenderInBrowserAbortSignal(): AbortSignal { const controller = new AbortController() controller.abort(new BailoutToCSRError('Render in Browser')) return controller.signal } /** * In a prerender, we may end up with hanging Promises as inputs due them * stalling on connection() or because they're loading dynamic data. In that * case we need to abort the encoding of arguments since they'll never complete. */ export function createHangingInputAbortSignal( workUnitStore: WorkUnitStore ): AbortSignal | undefined { switch (workUnitStore.type) { case 'prerender': const controller = new AbortController() if (workUnitStore.cacheSignal) { // If we have a cacheSignal it means we're in a prospective render. If // the input we're waiting on is coming from another cache, we do want // to wait for it so that we can resolve this cache entry too. workUnitStore.cacheSignal.inputReady().then(() => { controller.abort() }) } else { // Otherwise we're in the final render and we should already have all // our caches filled. We might still be waiting on some microtasks so we // wait one tick before giving up. When we give up, we still want to // render the content of this cache as deeply as we can so that we can // suspend as deeply as possible in the tree or not at all if we don't // end up waiting for the input. scheduleOnNextTick(() => controller.abort()) } return controller.signal case 'prerender-client': case 'prerender-ppr': case 'prerender-legacy': case 'request': case 'cache': case 'private-cache': case 'unstable-cache': return undefined default: workUnitStore satisfies never } } export function annotateDynamicAccess( expression: string, prerenderStore: PrerenderStoreModern ) { const dynamicTracking = prerenderStore.dynamicTracking if (dynamicTracking) { dynamicTracking.dynamicAccesses.push({ stack: dynamicTracking.isDebugDynamicAccesses ? new Error().stack : undefined, expression, }) } } export function useDynamicRouteParams(expression: string) { const workUnitStore = workUnitAsyncStorage.getStore() if (workUnitStore) { switch (workUnitStore.type) { case 'prerender-client': case 'prerender': { const fallbackParams = workUnitStore.fallbackRouteParams if (fallbackParams && fallbackParams.size > 0) { // We are in a prerender with cacheComponents semantics. We are going to // hang here and never resolve. This will cause the currently // rendering component to effectively be a dynamic hole. React.use(makeHangingPromise(workUnitStore.renderSignal, expression)) } break } case 'prerender-ppr': { const fallbackParams = workUnitStore.fallbackRouteParams if (fallbackParams && fallbackParams.size > 0) { const workStore = workAsyncStorage.getStore() if (!workStore) { throw new InvariantError( 'Missing workStore in useDynamicRouteParams' ) } return postponeWithTracking( workStore.route, expression, workUnitStore.dynamicTracking ) } break } case 'cache': case 'private-cache': throw new InvariantError( `\`${expression}\` was called inside a cache scope. Next.js should be preventing ${expression} from being included in server components statically, but did not in this case.` ) case 'prerender-legacy': case 'request': case 'unstable-cache': break default: workUnitStore satisfies never } } } const hasSuspenseRegex = /\n\s+at Suspense \(\)/ const hasSuspenseAfterBodyOrHtmlRegex = /\n\s+at (?:body|html) \(\)[\s\S]*?\n\s+at Suspense \(\)/ const hasMetadataRegex = new RegExp( `\\n\\s+at ${METADATA_BOUNDARY_NAME}[\\n\\s]` ) const hasViewportRegex = new RegExp( `\\n\\s+at ${VIEWPORT_BOUNDARY_NAME}[\\n\\s]` ) const hasOutletRegex = new RegExp(`\\n\\s+at ${OUTLET_BOUNDARY_NAME}[\\n\\s]`) export function trackAllowedDynamicAccess( workStore: WorkStore, componentStack: string, dynamicValidation: DynamicValidationState, clientDynamic: DynamicTrackingState ) { if (hasOutletRegex.test(componentStack)) { // We don't need to track that this is dynamic. It is only so when something else is also dynamic. return } else if (hasMetadataRegex.test(componentStack)) { dynamicValidation.hasDynamicMetadata = true return } else if (hasViewportRegex.test(componentStack)) { dynamicValidation.hasDynamicViewport = true return } else if (hasSuspenseAfterBodyOrHtmlRegex.test(componentStack)) { // This prerender has a Suspense boundary above the body which // effectively opts the page into allowing 100% dynamic rendering dynamicValidation.hasAllowedDynamic = true dynamicValidation.hasSuspenseAboveBody = true return } else if (hasSuspenseRegex.test(componentStack)) { // this error had a Suspense boundary above it so we don't need to report it as a source // of disallowed dynamicValidation.hasAllowedDynamic = true return } else if (clientDynamic.syncDynamicErrorWithStack) { // This task was the task that called the sync error. dynamicValidation.dynamicErrors.push( clientDynamic.syncDynamicErrorWithStack ) return } else { const message = `Route "${workStore.route}": A component accessed data, headers, params, searchParams, or a short-lived cache without a Suspense boundary nor a "use cache" above it. See more info: https://nextjs.org/docs/messages/next-prerender-missing-suspense` const error = createErrorWithComponentOrOwnerStack(message, componentStack) dynamicValidation.dynamicErrors.push(error) return } } /** * In dev mode, we prefer using the owner stack, otherwise the provided * component stack is used. */ function createErrorWithComponentOrOwnerStack( message: string, componentStack: string ) { const ownerStack = process.env.NODE_ENV !== 'production' && React.captureOwnerStack ? React.captureOwnerStack() : null const error = new Error(message) error.stack = error.name + ': ' + message + (ownerStack ?? componentStack) return error } export enum PreludeState { Full = 0, Empty = 1, Errored = 2, } export function logDisallowedDynamicError( workStore: WorkStore, error: Error ): void { console.error(error) if (!workStore.dev) { if (workStore.hasReadableErrorStacks) { console.error( `To get a more detailed stack trace and pinpoint the issue, start the app in development mode by running \`next dev\`, then open "${workStore.route}" in your browser to investigate the error.` ) } else { console.error(`To get a more detailed stack trace and pinpoint the issue, try one of the following: - Start the app in development mode by running \`next dev\`, then open "${workStore.route}" in your browser to investigate the error. - Rerun the production build with \`next build --debug-prerender\` to generate better stack traces.`) } } } export function throwIfDisallowedDynamic( workStore: WorkStore, prelude: PreludeState, dynamicValidation: DynamicValidationState, serverDynamic: DynamicTrackingState ): void { if (prelude !== PreludeState.Full) { if (dynamicValidation.hasSuspenseAboveBody) { // This route has opted into allowing fully dynamic rendering // by including a Suspense boundary above the body. In this case // a lack of a shell is not considered disallowed so we simply return return } if (serverDynamic.syncDynamicErrorWithStack) { // There is no shell and the server did something sync dynamic likely // leading to an early termination of the prerender before the shell // could be completed. We terminate the build/validating render. logDisallowedDynamicError( workStore, serverDynamic.syncDynamicErrorWithStack ) throw new StaticGenBailoutError() } // We didn't have any sync bailouts but there may be user code which // blocked the root. We would have captured these during the prerender // and can log them here and then terminate the build/validating render const dynamicErrors = dynamicValidation.dynamicErrors if (dynamicErrors.length > 0) { for (let i = 0; i < dynamicErrors.length; i++) { logDisallowedDynamicError(workStore, dynamicErrors[i]) } throw new StaticGenBailoutError() } // If we got this far then the only other thing that could be blocking // the root is dynamic Viewport. If this is dynamic then // you need to opt into that by adding a Suspense boundary above the body // to indicate your are ok with fully dynamic rendering. if (dynamicValidation.hasDynamicViewport) { console.error( `Route "${workStore.route}" has a \`generateViewport\` that depends on Request data (\`cookies()\`, etc...) or uncached external data (\`fetch(...)\`, etc...) without explicitly allowing fully dynamic rendering. See more info here: https://nextjs.org/docs/messages/next-prerender-dynamic-viewport` ) throw new StaticGenBailoutError() } if (prelude === PreludeState.Empty) { // If we ever get this far then we messed up the tracking of invalid dynamic. // We still adhere to the constraint that you must produce a shell but invite the // user to report this as a bug in Next.js. console.error( `Route "${workStore.route}" did not produce a static shell and Next.js was unable to determine a reason. This is a bug in Next.js.` ) throw new StaticGenBailoutError() } } else { if ( dynamicValidation.hasAllowedDynamic === false && dynamicValidation.hasDynamicMetadata ) { console.error( `Route "${workStore.route}" has a \`generateMetadata\` that depends on Request data (\`cookies()\`, etc...) or uncached external data (\`fetch(...)\`, etc...) when the rest of the route does not. See more info here: https://nextjs.org/docs/messages/next-prerender-dynamic-metadata` ) throw new StaticGenBailoutError() } } }